500g unsalted butter
400g milk chocolate chips and 400g dark chocolate chips, divided
170g dark chocolate
6 extra-large eggs
3 tablespoons instant coffee granules
2 tablespoons pure vanilla extract
500g caster sugar
160g plain flour, divided
1 tablespoon baking powder
1 teaspoon salt
200g smooth peanut butter
How to Cook
Preheat the oven to 170 degrees C. Butter and flour a 12 by 18 by 1 1/2-inch sheet pan.
Melt together the butter, 250g of both milk and dark chocolate chips (500g total), and the extra 170g dark chocolate in a medium bowl over simmering water. Allow to cool slightly. In a large bowl, stir (do not beat) together the eggs, coffee granules, vanilla, and sugar. Stir the warm chocolate mixture into the egg mixture and allow to cool to room temperature.
In a medium bowl, sift together 130g of flour, the baking powder, and salt. Add to the cooled chocolate mixture. Toss the remaining 150g of milk and dark chocolate chips (300g total) in a medium bowl with 30g of flour, then add them to the chocolate batter. Pour into the prepared sheet pan. Spoon the peanut butter over the top of the chocolate mixture and using a knife, swirl it through the chocolate mixture.
Bake for 20 minutes, then rap the baking sheet against the oven shelf to force the air to escape from between the pan and the brownie dough. Bake for about 10 to 15 minutes more or until a toothpick comes out clean. Do not overbake! Allow to cool thoroughly, refrigerate, and cut into large squares.